Class 9 Mathematics Chapter 6 Measuring Space: Perimeter and Area – Revision Notes

Quick revision notes for Class 9 Maths Chapter 6 (Measuring Space: Perimeter and Area). These Class 9 Mathematics Chapter 6 notes are ideal for quick revision just before exams.

Basic Formulas

• Rectangle: P=2(l+b), A=l×b.
• Square: P=4s, A=s².
• Parallelogram: A=base×height.

Heron’s Formula

• s = (a+b+c)/2 (semi-perimeter).
• Area = √[s(s−a)(s−b)(s−c)].
• Use when only side lengths known (no height).

Quadrilateral Area

• Split via diagonal into 2 triangles; sum their areas.

One-Line Summary

Heron’s formula finds a triangle’s area from its three sides alone (via the semi-perimeter), and quadrilateral areas can be found by splitting into two triangles along a diagonal.

Written by Satish

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